Synchronization method and means



Dec. 31, 1940. V SCHLES'JNGE-R 2,227,028

SYNCHRONIZA'IIO'N "METHOD AND MEANS Filed Jan. 17, I938 Javenior:

Patented Dec. 31, 1940 nrrs s'rrss Kurt Schlesinger, Berlin, Germany,assignor, by

mesne assignments, to Loewe Radio, Inc., a corporation of New YorkApplication January 17, 1938, Serial No. 185,363 In Germany January 20,1937 1 Claim.

It is known that upon the reception of interlaced line transmissions afrequent fault which is very difficult to be avoided consists in thefact that the two part images do not fit exactly one 5 within the other.This fault is perceived by the eye even when the displacement does notsurpass a few percents and creates the impression as if the picturewould contain merely half the number of lines.

This fault is caused by the fact that very slight traces of the linesynchronization signals are still present at the moment when the nextframe change impulse begins, and penetrate to the frame changesynchronization channel. In the interlaced line method employing an oddnumber of lines the frame change impulses takes place alternately atonce with a line impulse and with the middle between tWo line impulses.A residual trace of the line impulse accordingly has an unequal effectin both cases and, consequently, disturbs the symmetry of the frames.The usual method of separating both signals from another by tuning thetransformers initiating the respective relaxation oscillatorsapproximately to the frequency of the respective signals is insuificientto avoid the described fault.

The subject matter of the present invention is a method and means toavoid the described fault and consists in an improvement of theseparation of both signals, more particularly in means for preventingthe line signals to penetrate into the frame synchronizing channel, moreparticularly means in a time circuit inserted in the lead to the framesignal transformer,

The invention will be fully understood from the detailed descriptionwhich will now be given of an exemplary embodiment thereof which isillustrated in the accompanying drawing which shows a diagram of areceiver connection.

In the drawing there is shown by way of example a receiver diagram whichrealises in practice the fundamental idea of the invention.

The mixed signals are picked up by the receiver 5. By means of anamplitude filter, for 45 example the detector 6, the synchronizationimpulses are separated from the video signals. The latter are conductedvia lead 1 to the image receiver, tube I 3. The line impulses pass tothe line transformer 8 and are conducted to the line 50 synchronizationapparatus l4 whilst the image change signals are first conducted to afiltering member, which may consist of a resistance 9 and a condenserID. If this time circuit is approximately dimensioned (50,000 ohms and1,000 cm.), a time constant of approximately 10 sec. which approximatelycorresponds to a line period of a 5 400-line image effects the desiredfiltering effect.

The frame change impulses are further conducted, via a safety resistanceH, to the transformer l2 which is tuned approximately to the duration ofthe image impulses and is connected 10 with the frame changesynchronization apparatus IS. The resistance ll prevents an inductivereaction of the primary winding of 12 on the time circuit 9/10 andamounts to approximately 50,000

15 ohms.

All leads and apparatus carrying line impulses must be completelyscreened off against all leads carrying frame change impulses.

I claim: 20

In a television receiver, means to receive picture and synchronizingsignals wherein the synchronizing signals follow a predetermined timesequence of picture signals and the synchronizing signals comprise lineand frame synchronizing 2 signals each of substantially like amplitudeand different duration, detector means for separating the synchronizingsignals from the combined picture and synchronizing signal energy, atransformer tuned to the frequency of the line syn- 30 chronizingsignals connected to the output of the detector to separate the linesynchronizing signals from the frame synchronizing signals, a secondtransformer tuned to the frequency of the frame synchronizing signalsalso connected to the output of the detector to separate the framesynchronizing signals from the line synchronizing signals, a time delaycircuit comprising a series resistance element and a shunt capacityelement connected between the detector and the frame signal separatingtransformer for delaying the frame synchronizing signal by apredetermined time delay relative tothe period between two successiveline synchronizing impulses, resistance means connected between thesecond transformer and the time delay circuit for preventing reaction ofthe transformer upon the time delay circuit, and a relaxation oscillatormeans connected to receive the output energy from each of thetransformers.

KURT SCHLESINGER.

